Pitch one might offer t-shirt conditions, but that doesn’t mean you’ll find “sun’s out, guns out” weather on pitch four, too. “It was 80 degrees and sunny when I placed my first cam,” says one tester of a late summer climb at Colorado’s Lumpy Ridge, “and then a half hour later, I was shivering in a whipping wind.” Solution? This 2-oz. wonder that packs down to the size of a golf ball. The seven-denier nylon shell blocked warmth-robbing wind well enough that our tester used it on winter training runs. It’s not breathable (and only water resistant), but the quarter-zip allows adequate venting. Three-season only—no pockets, and only thin layers fit beneath.